Rich.. "This increased the size to about 220 gallons."?????? you mean
increased to 2200 gallons?

I am in zone 5-6, 10 below in winter, sometimes -20. I too cover the
pond with plastic to minimize evaporation which carries the heat away.
In addition, I constructed my pond with a stud wall that is insulated,
altho if I do it again I will use blow in expanding foam which is
water proof and seals really well.. wood is a very good insulator,
BTW. the bottom of the pond is only insulated with the carpet foam
stuff. actually it is pretty good insulation. My pond stays 50-55 for
all but 1 coldest month with a single 500 watt heater. And my pond is
1.5 feet above ground.
This year the pond is going to have double plastic since I am
enclosing the area around the pond (for sitting) and enclosing the
pond itself with a little lean to.
http://weloveteaching.com/mypond/winters/winter.htm
Ingrid

On Mon, 18 Jun 2007 06:43:06 CST, "RichToyBox"
wrote:
You don't say where you are located or what depth the ground will freeze in
your area, so I will give my general feelings. I have two ponds, one 4000
gallons and one 3500 gallons that are both heated to around 70F (20C). The
most important thing that you can do to heat a pond is to put some type of a
cover on it to minimize evaporation. Evaporation really cools the pond. I
cover mine with a lean-to structure that can be seen at
http://www.geocities.com/richtoybox/pondpage3.html. This structure gets
covered with a solar swimming pool blanket that looks like bubblewrap and
two layers of polyethylene sheeting. It accumulates some solar heating and
helps retain the heat in the pond. The earth at a couple feet below the
frost line is pretty constant temperature around 50 degrees F (10C). This
relatively warm earth will act as a heat source if the pond temperature
falls to below this temperature, so I don't like to see it insulated. The
walls of the pond, near the surface might benefit from some insulation,
since the frozen soil would rob more heat from the pond.